The eGFR, or estimated glomerular filtration rate, is a measurement that evaluates kidney function by estimating the amount of blood filtered by the kidneys. The kidneys contain tiny filters called glomeruli that are responsible for removing waste products from the blood. If these filters fail to work properly, kidney function can be affected. The eGFR is calculated using a person's age, gender, ethnicity, and serum creatinine levels to provide an estimate of their actual glomerular filtration rate.